Involucrin (hINV) acts as an important amine donor and is crosslinked to various amine acceptors by transglutaminase to assemble the cornified envelope. hINV is among the first proteins deposited and functions as a scaffolding for subsequent protein and lipid deposition. Appropriate hINV deposition is required for maintenance of barrier function. Involucrin expression is confined to external surface epithelial cells. It is expressed suprabasally in epidermis, and expression is altered in disease. To understand normal and abnormal epidermal differentiation, it is essential to understand the mechanisms that regulate epidermal gene expression. Involucrin is an advanced model for the study of gene regulatory mechanisms in epidermis. We are now positioned to address fundamental questions about the DNA sequences and transcription factor complexes that drive tissue-specific and differentiation-appropriate hINV expression in vivo. Our recent studies identify a region of the hINV gene upstream regulatory region, the distal regulatory region (DRR) that is required for differentiation-appropriate hINV gene expression. We have shown that the DRR contains spatially distinct elements that cooperate to regulate gene expression during differentiation. In addition, we have identified a specific AP1 site as a required participant in this regulation. We are now prepared to examine the composition of the multiprotein complex that forms at these sites and how this complex influences in vivo gene expression. The major goal of this proposal is to identify the transcription factors that bind within the DRR to regulate tissue-specific and differentiation-appropriate expression. These studies are designed to provide important new insights regarding the mechanisms that regulate gene expression during epidermal differentiation.